Thiocyanate as a marker of saliva in gastric juice?

One source of error in gastric secretion studies is swallowed saliva. The possibility that salivary thiocyanate might be used to measure this contamination has been investigated. Thiocyanate concentration was measured in saliva and gastric juice collected simultaneously in 22 duodenal ulcer patients undergoing routine insulin and histamine secretion studies. On stimulation, despite the increase in the rate of gastric secretion this was not matched by an appropriate fall in the concentration of thiocyanate in gastric juice. Moreover, in one-third of the gastric juice specimens, the thiocyanate concentration was greater than in the simultaneous samples of saliva. Thus, contrary to what has been claimed, thiocyanate is present not only in saliva but also in gastric juice. Therefore it cannot be used as a marker of salivary contamination. An adequate marker of this source of error has not yet been found.